With development of network technology, more and more people get their desired information over the network. For example, users may get news information over the network, or may get information of audio-video files over the network, etc. There are videos on various subjects on the network. Video-on-demand is a widely used type of service for users who wish to watch a video. For example, when a user wishes to watch a certain film, the user may search the corresponding film on a video website, and the website, after receiving a click-to-play instruction from the user, may pull data from a server to play the film. Since the video-on-demand service requires users to select a file to play, it causes a high cost on interaction.